Field
The present application relates generally to wireless communications, and more specifically to methods and systems for acquisition of wireless communication with a femtocell unit.
Background
Wireless communication systems are widely deployed to provide various types of communication (e.g., voice, data, multimedia services, etc.) to multiple users. As the demand for high-rate and multimedia data services rapidly grows, there lies a challenge to implement efficient and robust communication systems with enhanced performance.
In recent years, users have started to replace fixed line broadband communications with mobile broadband communications and have increasingly demanded great voice quality, reliable service, and low prices, especially at their home or office locations.
In addition to the mobile phone networks currently in place, a new class of small base stations has emerged, which may be installed in a user's home or office and provide enhanced indoor wireless coverage to mobile units using existing broadband Internet connections. Such personal miniature base stations are generally known as femtocells, or, alternatively, access point base stations, Home Node B (HNB), or Home eNode B (HeNB). Typically, such miniature base stations are connected to the Internet and the mobile operator's network via DSL router or cable modem, thus providing connectivity between the user's UE and the Internet.
In wireless communication networks, a mobile station, access terminal (AT) or user equipment (UE) typically scans a defined frequency spectrum to identify one or more access nodes (e.g., macrocells, microcells, picocells, femtocells, base stations, etc.) through which it may obtain wireless communication service. This is often referred to as system acquisition, and typically happens when the UE is powered on after being off for some time, when the UE recovers from lack of coverage, or when it switches between two different networks (e.g., 2G and 3G networks). In these cases, the UE generally searches through a list of carrier frequency candidates. For each frequency, the UE may attempt to detect a preamble or acquire a scrambling code and phase of a carrier signal from the strongest base station detected or found. The length of the frequency list depends on the actual scenario. For example, if the UE has been moved outside its home coverage area (e.g., service region, state, city, country, etc.) while it was powered off, then the frequency list can be quite long. Most often, the correct carrier frequency is not known and the frequency scanning process involves a coarse frequency scan where a frequency band may be identified followed by fine frequency scan where particular channels within the frequency band may be scanned. Cell or base station acquisition may then be done on each channel where energy is found during the fine frequency scan. During the cell acquisition, the UE searches for service both in frequency and code space, which is typically an undesirably large number of hypotheses or combinations to search. Once an appropriate base station is selected, the UE is ready to communicate signaling messages to establish a data and/or voice session via the selected base station.
Due to the scanning performed by the UE to identify access nodes and acquire a scrambling code and phase, the acquisition process may take a noticeably long time. Consequently, a way to expedite and/or improve the acquisition process would be beneficial.